issues setting up apache config for reverse proxy

[KBlixt]

I'm trying to set up a document server behind a apache reverse proxy and I'm really stuck. I've tried the configs that's here: https://helpcenter.onlyoffice.com/server/document/document-server-proxy.aspx but to no avail.
I'll just post my config here and maybe someone can point out what I'm doing wrong... all I'm getting when I'm accessing mysite.com/documents is the default page of nextcloud...

nextcloud is hosted on 192.168.0.100:9999 and onlyoffice is working when accessing it on 192.168.0.100:8888

help :(

<IfModule mod_ssl.c>
	<VirtualHost *:80>
		ServerName mysite.com
		ServerAdmin admin
		
		RewriteEngine On

		ProxyRequests     Off
		ProxyPreserveHost On

		ProxyPass "/" "http://127.0.0.1:9999/"
		ProxyPassReverse "/" "http://127.0.0.1:9999/"

		RewriteEngine On
		RewriteCond %{SERVER_PORT} !443
		#RewriteCond %{REQUEST_URI} !^\/login\/flow
		RewriteRule ^(/(.*))?$ https://%{HTTP_HOST}/$1 [R=301,L]
	</VirtualHost>

	<VirtualHost *:443>
		ServerName mysite.com
		ServerAdmin admin

		SSLCertificateFile /filepath/fullchain.pem
		SSLCertificateKeyFile /filepath/privkey.pem
		Include /etc/letsencrypt/options-ssl-apache.conf

		ProxyRequests     Off
		ProxyPreserveHost On

		ProxyPass "/" "http://127.0.0.1:9999/"
		ProxyPassReverse "/" "http://127.0.0.1:9999/"

		<Location /sabnzbd>
			order deny,allow
			deny from all
			allow from all
			ProxyPass http://localhost:8080/sabnzbd
			ProxyPassReverse http://localhost:8080/sabnzbd
		</Location>

		Define VPATH /documents
		Define DS_ADDRESS 192.168.0.100:8888

		<Location ${VPATH}>
			Require all granted
			SetEnvIf Host "^(.*)$" THE_HOST=$1
			RequestHeader setifempty X-Forwarded-Proto http
			RequestHeader edit X-Forwarded-Host (.*) $1${VPATH}
			ProxyAddHeaders Off
		</Location>

		ProxyPassMatch ^\${VPATH}(.*)(\/websocket)$ "ws://${DS_ADDRESS}/$1$2"
		ProxyPass ${VPATH} "http://${DS_ADDRESS}"
		ProxyPassReverse ${VPATH} "http://${DS_ADDRESS}"

	</VirtualHost>
</IfModule>

[RolandBBerlin]

I set up my configuration using a separate (virtual) document server. My nextcloud server is hosting nextcloud, but also performs reverse proxy for the document server.
The socument server has a separate subdomain (documentserver.mydomain) with its own certificate. The document server is set without ssl, so the reverse proxy is handling ssl-encapsulation of requests.
That said, my complete site configuration for the document server looks like this:
('server-address' - public domain name of document server, 'backendserver-address' - address and port by which the proxy server can access the document server).

<VirtualHost *:80>
    ServerAdmin admin
    ServerName server-address

    RewriteEngine on
    RewriteCond %{SERVER_NAME} =server-addres
    RewriteRule ^ https://%{SERVER_NAME}%{REQUEST_URI} [END,NE,R=permanent]
</VirtualHost>

<VirtualHost *:443>
    ServerAdmin admin
    ServerName server-address

    SSLEngine on
    SSLCompression off
    SSLHonorCipherOrder on
    SSLCipherSuite EECDH+AESGCM:EDH+AESGCM:AES256+EECDH:ECDHE-RSA-AES128-SHA:DHE-RSA-AES128-GCM-SHA256:AES256+EDH:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-SHA384:ECDHE-RSA-AES128-SHA256:ECDHE-RSA-AES256-SHA:DHE-RSA-AES256-SHA256:DHE-RSA-AES128-SHA256:DHE-RSA-AES256-SHA:DHE-RSA-AES128-SHA:ECDHE-RSA-DES-CBC3-SHA:EDH-RSA-DES-CBC3-SHA:AES256-GCM-SHA384:AES128-GCM-SHA256:AES256-SHA256:AES128-SHA256:AES256-SHA:AES128-SHA:DES-CBC3-SHA:HIGH:!aNULL:!eNULL:!EXPORT:!DES:!MD5:!PSK:!RC4

    SSLProtocol All -SSLv2 -SSLv3
    SSLCompression off
    SSLHonorCipherOrder on

    SetEnvIf Host "^(.*)$" THE_HOST=$1
    RequestHeader setifempty X-Forwarded-Proto https
    RequestHeader setifempty X-Forwarded-Host %{THE_HOST}e
    ProxyAddHeaders Off

    ProxyPassMatch (.*)(\/websocket)$ "ws://backendserver-address/$1$2"
    ProxyPass / http://backendserver-address/
    ProxyPassReverse / http://backendserver-address/

    SSLCertificateFile "{{SSL_CERTIFICATE_PATH}}"
    SSLCertificateKeyFile "{{SSL_KEY_PATH}}"
</VirtualHost>

Good luck!
Roland